This invention relates to a gas spring of the type comprising a cylinder which is closed at one end and open at the other and having a piston slidable in the cylinder and connected to a rod which projects into the cylinder through the open end thereof. The open end of the cylinder is sealed by a sealing assembly including an annular flexible member which normally is in sealing engagement with the rod and with the inner wall of the cylinder. In the cylinder is a quantity of oil and a gas under pressure.